Tempered glass sheets have been used as windowpanes (particularly as side windowpanes or rear windowpanes) for automobiles. A tempered glass sheet has compressive stress layers at its surfaces (at a first surface and a second surface) and a tensile stress layer at a center portion in its thickness direction. Such a tempered glass sheet can be produced by applying tempering treatment by blowing air to the surfaces of a glass sheet in a high temperature state of from 650 to 700° C.
In recent years, from the viewpoint of environmental problems, in order to save the costs for fuels, reduction of the weight of automobiles has been strongly demanded, and reduction of the weight of the windowpanes for automobiles, as automobile parts, has been desired.
Patent Document 1 discloses a tempered glass which is an air-quench tempered glass sheet having a thickness of from 2.5 to 3.1 mm and which satisfies that in the fragmentation test (JIS R3212: 2008) in a size of 50×50 mm, as stipulated in Safety Standards for Automotive glass, the number of fragments is at least 40 pieces (hereinafter referred to also as the fragmentation quality) and that in the impact strength test (JIS R3212: 2008) to be judged by a height for breakage by dropping a steel ball of 227 g, the height is at least 2 m (hereinafter referred to also as the impact strength quality).